Other Important Taxa PDF

M.A. Freeman Parasites of veterinary importance Helminths: parasitic worms, large and multicellular The term "helminth" includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities: -they are vermiform or “worm-like” in form- Phylum Nematoda (roun...

M.A. Freeman Parasites of veterinary importance Helminths: parasitic worms, large and multicellular The term "helminth" includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities: -they are vermiform or “worm-like” in form- Phylum Nematoda (roundworms) Phylum Platyhelminthes (flatworms) – Class Cestoda (tapeworms) – Class Trematoda (flukes: endoparasites) – Class Monogenea (skin flukes: ectoparasites) – Class Turbellaria (free-living flatworms, some parasitic forms) Phylum Acanthocephala (thorny-headed worms) Phylum Annelida (segmented worms) not parasitic (leeches) Class: Monogenea – ectoparasitic flatworms ▪ Part of the Phylum Platyhelminthes ▪ Ectoparasites: especially on the skin, fins and gills of fish, also in exotics like frogs and reptiles and hippos! (in the eye) ▪ No true body cavity or coelom ▪ Can be quite large 2-3 cm or microscopic e.g. Gyrodactylus ▪ Simple digestive system: mouth pharynx and intestine, no anus (flame cells are specialized excretory cells found in the simplest freshwater invertebrates, including flatworms) ▪ Poorly developed suckers, attachment is via hooks (classification) ▪ Hermaphroditic, mostly producing eggs, some are viviparous ▪ Ancestrally related to Turbellaria (free-living flatworms) and closest to modern cestodes Class: Monogenea – ectoparasitic flatworms Direct life cycle leads to significant problems in cage culture of fish Oncomiracidium Class: Monogenea – ectoparasitic flatworms Gyrodactylus: viviparous monogeneans and some species are extremely pathogenic Ｍonogenea: Benedenia seriolae of amberjacks Feeding on epithelial cells of the skin Up to 1 cm long Monogenea Pseudorhabdosynochus sp. of a grouper = feeding epithelial cells Eggs with long filament Parasites of veterinary importance Helminths: parasitic worms, large and multicellular The term "helminth" includes a number of phyla, many of which are unrelated (phylogenetically) but they have superficial similarities: -they are vermiform or “worm-like” in form- Phylum Nematoda (roundworms) Phylum Platyhelminthes (flatworms) – Class Cestoda (tapeworms) – Class Trematoda (flukes: endoparasites) – Class Monogenea (skin flukes: ectoparasites) – Class Turbellaria (free-living flatworms, some parasitic forms) Phylum Acanthocephala (thorny-headed worms) Phylum Annelida (segmented worms) not parasitic (leeches) Phylum Acanthocephala– thorny-headed worms http://tolweb.org/Acanthocephala/20452 The earliest recognisable description of Acanthocephala – a worm with a proboscis armed with hooks – was made by Italian author Francesco Redi (1684) Acanthocephalans are highly adapted parasites, and have lost many organs and structures through evolutionary processes, making direct comparative taxonomy difficult. No mouth or digestive system, as in cestodes but they are not related Nutrient are absorbed from hosts’ digested gut contents, via the integument Can be quite large over 10 cm Phylum Acanthocephala– thorny-headed worms Recent genomic data suggests sister group to rotifers: freshwater zooplankton Invertebrate intermediate host Adult stage almost always in the digestive tract, not usually pathogenic Acanthocephala are sexually dioecious (an individual organism is either male or female) Phylum Acanthocephala– thorny-headed worms All have complex life cycles Many not host specific Infect Invertebrates Birds Amphibians Fish Mammals Diagnosis by observation of eggs in feces Acanthocephaliasis (presence of parasite, sub-clinical) Phylum Acanthocephala– thorny-headed worms Recent case study at RUSVM Unusual cysts were found in the skeletal muscle of mongoose used in a leptospirosis trial Unusual morphology and were not readily identifiable by parasitologists or pathologists Used light microscopy to look for microscopic detail Amplify DNA from various rRNA gene regions to try to identify Later similar cysts were seen in monkeys Cystacanth stage inverted monkey scrotum Phylum Acanthocephala– thorny-headed worms The cystacanth is a resting stage, where the parasite lies encysted No further development occurs in this host, normally an invertebrate The cystacanth must be ingested by its definitive host, usually a vertebrate Problem, mongoose and monkey are vertebrates!! Help….DNA So why is this not in the intestine and an adult stage?? ITS sequencing provided the information needed Cystacanths from both mongoose and monkey are the same species Also we had a direct hit in the DNA databases almost 100% identity Oncicola venezuelensis This raises some interesting questions! What is the definitive host in St Kitts? Domestic cat? (a cat eating a mongoose or a monkey!) Are mongoose and monkey intermediate hosts or paratenic hosts or dead end hosts? Oncicola venezuelensis from the ocelot in Brazil In Brazil, the intermediate host of Oncicola venezuelensis is unknown. Cystacanths have been recovered and described in Caribbean termites, in subcutaneous nodules of lizards Anolis cristatellus, in the Indian mongoose Herpestes auropunctatus and in pearlyeyed thrashers Margarops fuscatus For final development to the adult stage in St Kitts, a cat is probably required to eat the cystacanths, so some hosts are probably a dead end Acanthocephala Thorny-headed worms, worm-like but not related to the other taxa like nematodes and Platyhelminthes Actually related to rotifers They are sexually dioecious (an individual organism is either male or female) Have complex life cycles, adults almost always in the intestine, can be quite large >10 cm (not usually pathogenic) Many not host specific especially in the intermediate hosts Highly adapted parasites, no mouth, absorb via cuticle Example Oncicola venezuelensis (final host a felid (ocelot) in native range) In St Kitts, some hosts are likely to be dead-end hosts, such as the mongoose and monkey Mongoose and monkey are not final hosts as the cystacanth stage is found encysted in the muscle and not developing into an adult in the intestine Parasite of veterinary importance Kingdom Protozoa (Protists) – – – Phylum Mastigophora (flagellates) Phylum Apicomplexa Phylum Ciliophora (ciliates) Kingdom Fungi Kingdom Animalia – – Phylum Arthropoda (insects/arachnids, copepods) Phylum Cnidaria (Myxozoa) The MYXOZOA Mark A. Freeman Polar capsule/filaments are used in sporoplasm release. ‘evolved/derived nematocyst’ Myxozoa (Class: Myxosporea): Phylum Cnidaria Myxozoa are highly adapted parasitic cnidarians Indirect life-cycle Fish host myxospore actinospore Annelid host (oligochaete / polychaete) Myxobolus cerebralis and whirling disease Disease first described in Germany in 1898 (Hofer) Destruction of cartilage (especially spinal column and cranium) in juvenile salmonids; massive infection leads to death of fish or life-long skeletal deformities. Characteristic erratic tail chasing behaviour (“whirling disease”) and blackened caudal area due to damage of the CNS due to infection of the cartilage. Rainbow trout are considered the most susceptible of 11 salmonid hosts; losses may reach 90%; Parasite has been spread by movements of live or frozen fish from presumed origins in Eurasia to many countries in central and western Europe, Australia / New Zealand and the USA. Life-cycle elucidated; programs to minimise infection in hatchery-reared rainbow trout now active. https://www.youtube.com/watch?v=S5a0GrrymNo The Hepatic biliary group of myxosporeans: reveals infection with myxospores in other groups Reptiles: FW turtles Mammals: shrew/mole Birds: ducks / waterfowl Amphibians: frogs Representatives of genera of major myxospore morphotypes Presence of myxospores are still the defining diagnostic feature for myxosporean infections Finding a myxospore is diagnostic: it is not useful for species identification Grouping by host type & tissue tropism (predilection site) using DNA data Protacanthopterygii Escoiformes: Pikes Salmonids Elopomorpha: Eels, tarpon, ladyfish All urinary system Salmonids (nervous tissues) Hepatic biliary system Class: Malacosporea, Tetracapsuloides bryosalmonae Tetracapsuloides bryosalmonae is a myxozoan parasite of salmonid fish. It causes Proliferative Kidney Disease (PKD), one of the most serious parasitic diseases of salmonid populations in Europe and North America. Collapse of arctic char population in Iceland due to this parasite, as water temperatures have risen about 13C, and the parasite becomes pathogenic The Multivalvulida Order of histozoic marine myxosporeans (Kudoidae & Trilosporidae) Typically found in skeletal muscles of marine fish but have also been found in other organs such as brain, heart, gills, kidney, gall bladder, ovary and intestines, often still associated with muscle tissues. Have 3 or more shell valves, with apical polar capsules Mostly pathogenic as develop inside tissues (Histozoic) unlike many myxozoans that are ‘Coelozoic’ developing in coelom-like spaces, e.g. the gallbladder Images of Kudoa islandica The Multivalvulida- Kudoa Cause significant losses to commercial catches of wild fish species due to presence of white cysts in the muscle and may cause post mortem myoliqufaction of fish fillets. Kudoa iwatai in red sea bream, Japan Kudoa thyrsites in olive flounder, Japan Kudoa amamiensis in yellowtail, Japan Kudoa thyrsites in Atlantic mackerel, UK The Multivalvulida- Kudoa There are serious food safety concerns over the consumption of some Kudoa-infected fish products Affected products cause food poisoning, with diarrhea and vomiting occurring a short time after Kudoa-infected fish is ingested. Known from flatfish (Paralichthys olivaceus), tuna (Thunnus spp.), and amberjack (Seriola dumerili) all of which have occurred nationwide in Japan, and in Korea. More recently from Pacific bluefin tuna Kudoa hexapunctata from the somatic muscle of wild Pacific bluefin tuna Thunnus orientalis Kudoa septempunctata from the trunk muscle of cultured olive flounder (Paralichthys olivaceus) 7 PCs Images used with permission from Hiroshi Yokoyama University of Tokyo, Japan 6 PCs Facts to know about the Myxozoa After years of being described as protozoans, we now know that they are in fact parasitic jellyfish (Cnidaria) They are obligate parasites, with a two host life cycle, that has two different spore forms produced The all have polar capsules, which are used to help infect a new host, these are related to the stinging cells (nematocysts) in non-parasitic Cnidaria Some cause very serious diseases in commercial fish species, both farmed and wild Problematic species are typically histozoic being found inside host tissues Coelozoic forms are generally not pathogenic, just interesting! They also infect, some birds, amphibians, reptiles and some mammals Some species of Kudoa are known to cause human gastrointestinal problems when eaten in undercooked fish